The term “target” is used herein to denote a skin defect such as a vascular lesion, pigmented lesion, acne, unwanted hair or wrinkle. Selective thermal treatment of skin is commonly used in aesthetic medicine to remove skin targets. In order to be destroyed, the target must be raised to a temperature of about 70° C. without raising the temperature of the surrounding epidermis or dermis to damaging levels. The most popular method of thermal skin treatment is selective photo-thermolysis in which light energy produced by a laser or flash lamp is selectively absorbed by a pigmented portion of the target. However, with this method it is often not possible to heat the entire target to a temperature necessary for destroying it without heating the surrounding skin to damaging levels. The main problem is that the optical contrast between the target and the surrounding skin tissue is not high enough to obtain a significant difference in temperature between the target and the surrounding skin tissue.
U.S. Pat. No. 5,755,753 discloses use of the radio-frequency (RF) range of electro-magnetic energy for skin tightening, where RF energy is applied to a pre-cooled skin surface. U.S. Pat. No. 5,846,252 discloses treating hairs to reduce their electrical resistance and then applying RF current.